In switching power converters, such as synchronous boost converters or buck-boost converters, there is a high peak voltage at the V_LX node (input node) during the first dead time (DT1) when the low-side switching device has turned off an the high-side switching device has not yet turned on. The peak V_LX(peak) of this voltage depends on the output voltage and the parasitic inductance on the printed circuit board (PCB). The parasitic inductance and the inductor current dominate the V_LX (peak) during the first dead time DT1. This V_LX(peak) might damage the low-side switching device if the V_LX (peak) is higher than the breakdown voltage of the low-side switching device, especially if the parasitic inductance and the inductor current are both high. The peak voltage V_LX(peak) also impacts the life time and reliability of the low-side switching device.
One solution to this issue would be to use a low-side switching device with a higher breakdown voltage. However, higher voltage devices typically have a higher on-state resistance, which means that the area of the low-side switching device would have to be much larger to achieve the same converter efficiency.